Heteroleptic Ruthenium(II) Complexes of Phenanthroline-Based Ligands as Efficient Electrocatalysts for Oxygen Evolution Reaction

Electrocatalysis has emerged as a vital technique for addressing global energy demands and environmental sustainability. Despite significant progress over the past two decades, the development of efficient and durable electrocatalysts remains an ongoing challenge. In this work, we report the synthesis of four ruthenium(II) complexes ( Ru1, Ru2, Ru3, and Ru4 ) as potential electrocatalysts for the oxygen evolution reaction (OER) via water oxidation. All complexes were thoroughly characterized using various spectroscopic techniques and revealed notable electrocatalytic activity. Among all of the complexes, Ru3 demonstrated superior OER performance, attributed to its highly accessible surface sites and low charge-transfer resistance ( R ct = 25.99 ohm). Ru3 also delivered an impressive turnover frequency of 2.81 s –1 and a Tafel slope of 170.40 mV/dec, confirming its excellent catalytic efficiency. These findings highlight the promise of p-cymene-substituted heteroleptic Ru(II) polypyridyl complexes as next-generation OER catalysts and may contribute to advancing sustainable hydrogen production and the development of cost-effective electrocatalytic systems.